The long range objective of this project is to establish the theoretical and practical basis for the development of a porcelain fused to metal system for fixed prosthetic applications which will meet certain specified criteria. The specific aims of this study are to: I. determine porcelain adherence to alloys and establish the type of relationship between chemical diffusion and mechanical bonding using x-ray fluorescent analysis, S.E.M. and Electron Spectroscopic Chemical Analysis (ESCA); to determine diffusion characteristics and evaluate the three classes of porcelain failure using fractographic technics. II. study the effect of specified casting variables on nonprecious alloy casting fit, accuracy, and casting defects. Variables such as mold and metal temperature, sprue size, and investments will be studied. III. study the effect of current soldering procedures on the solder joint quality utilizing: a) tensile butt joint tests, and b) metallographic x-ray analysis, and S.E.M. examinations of solder joints for diffusion. IV. measure thermal expansion coefficients of metal and porcelain related to technique of manipulation of the materials. The effect of microstructure, composition, test specimen preparation, and thermal history of the specimens will be studied. V. attempt to develop reliable test methods for tarnish and corrosion using: electrochemical methods in relation to specific test solution composition, with special attention to alloy microstructure, composition, and crack or crevice configuration. VI. develop a screening criteria flow sheet using predetermined standards. Using this type methodology, one can quickly evaluate metal-porcelain combinations as to their clinical potential.